1. Field of the Invention
The present invention relates to a dental composition kit. Precisely, the invention relates to a dental composition kit, of which the cured product of the compositions well bonds to hard tissues such as tooth enamel in dentin, and which is therefore useful in restoring decayed or injured teeth and in bonding prostheses to teeth.
2. Description of the Related Art
For restoring decayed or injured teeth, widely used are amalgam, glass ionomer cement and composite resin. On the other hand, for bonding prostheses such as crowns, inlays and bridges to decayed or injured teeth, widely used are zinc phosphate cement, glass ionomer cement and composite resin cement. In that manner, various materials are used for restoring decayed or injured teeth, and one of them is glass ionomer cement.
The basic constituent components of glass ionomer cement are a polyalkenoic acid, water and an ion-leachable glass filler. Improving the properties of such glass ionomer cement by adding thereto some other components has been tried, for example, as in Japanese Patent Laid-Open Nos. 164807/1990, 6358/1990, 255033/1993, 26925/1996, and International Patent Publication Nos. 505868/1998, 506127/1998. The improved glass ionomer cement of those types is generally referred to as resin-modified glass ionomer cement, and has become popular in the recent year.
The basic principle in restoration of defective teeth is to fill an aesthetic material of certain strength in the cavity of defective teeth or in the space between a defective tooth and a prosthesis to thereby ensure the permanent function of the restored teeth, not to merely improve the function and the shape of the restored teeth for the moment, and it is to further ensure the prevention of caries recurring.
In general, it is known that glass ionomer cement releases fluorine effective for making teeth acid resistant from the viewpoint of caries prevention, but it should be understood that the fluorine release from it is only an auxiliary function of glass ionomer cement. Specifically, if the cause of secondary caries is not eliminated, fluorine release, if any, to reinforce teeth could not be the essential solution of caries. For essentially solving the problem of caries, it is first necessary to surely seal up the interface between a restored tooth and a prosthesis with cement. This is to prevent caries-causing bacteria from invading the aforesaid interface and to prevent food residues that may be the nutrients for the bacteria also from entering it, to thereby prevent secondary caries recurring. For it, the function of fluorine may be taken into consideration merely as an auxiliary preventive means for bonding failure in the restored tooth. As so reported in the Quintessence, Vol. 16, No. 4 (1997), pp. 69-72, secondary caries accounts for about 50% of the reason for re-restoration of teeth once restored with glass ionomer cement, and is significant. This is because of mistaking the means for the end in that fluorine only is expected for caries prevention.
In restoring decayed or injured teeth, it is desired to establish tight adhesion of a restorative to a tooth. For a technique increasing the bonding power of resin-modified glass ionomer cement to teeth, for example, Japanese Patent Laid-Open No. 249514/1997 discloses a primer composition.
Regarding the primer technique such as that disclosed in the laid-open patent specification, it is known that a combination of an organic peroxide, amine and a salt of a sulfinic acid is an effective polymerization initiator in bonding restoratives to teeth. However, when the constitutive ingredients of the initiator, an organic peroxide, amine and a salt of a sulfinic acid are blended in a primer, the primer must be a two-pack primer, as in the examples in Japanese Patent Laid-Open No. 249514/1997. Such a two-pack primer is troublesome in dental use in that the two packs must be mixed every time before use. If the two packs are mixed and the resulting mixture is left as it is for a while for some reason in dental treatment, the mixture will soon polymerize and cure, and will be useless. Even if the mixture does not polymerize to such an extent that it cure, the reaction of the constitutive ingredients progresses and the mixture will lose its effective function for bonding.
Further, the bonding power of dental cement to teeth is not indiscriminately determined only by the primer composition between the cement and a tooth. Specifically, the total composition of primer and cement must be taken into consideration to attain a higher level bonding of cement to teeth, because the reactivity of the two affect not a little the bonding power of cement to teeth.
To solve the problems noted above, we, the present inventors have assiduously studied various primer and cement compositions, especially the type of polymerization initiator to be used in the compositions and how the polymerization initiator is to be incorporated into them, and, as a result, have found a dental composition kit comprising a one-pack primer composition and a cement composition. When combinatorially used, the two compositions of the kit give high bond strength of restorative to tooth. On the basis of this finding, we have completed the present invention.